Various type of shipping containers have been developed including conventional cardboard cartons having an insulating material therein that may be formed into a desired shape or may comprise panels or the like. Generally, a coolant such as packaged ice, gel-packs or loose dry ice is placed around the product in a cavity to refrigerate the product during shipping.
With regard to shipping particularly sensitive products, such as certain medical or pharmaceutical products, rigid polyurethane containers often are used because of the superior thermal properties. Conventional insulated shipping containers have many problems, particularly when shipping temperature sensitive products for extended periods of time, such as when products are shipped internationally. These containers, especially modular liner systems, often include a number of seams in the insulating material through which air can enter and heat the cavity in the carton. In addition, the cavity often includes airspaces around the product and coolant which can facilitate but not control convection, especially if the insulating material includes leaking seams. Unfortunately, temperature gradients or zones are created. These conditions may accelerate the melting of the coolant, consequently shortening the time that the container can maintain a refrigerated condition. In addition, the cover may be formed from different material, such as polyester foam which may have a thermal resistance substantially lower than the body itself and thus may compromise the performance of the container.
Furthermore, the product and coolant typically are placed together within the cavity in a carton, which may have adverse effects. When shipping certain products it may be desired to refrigerate but not freeze the product. Placing a coolant, such as loose blocks of dry ice, into a cavity against the product may inadvertently freeze and damage the product. Even if held away from the product, the coolant may shift in the cavity during shipping, especially as it melts and shrinks in size, inadvertently contacting the product. In addition, melted coolant may leak from its container, possibly creating a mess within the cavity or even contaminating the product being shipped.
Some suitable solutions to some of the foregoing problems have been developed in the past such as shown and described in U.S. Pat. No. 5,924,302. Still, there are needs for containers particularly for shipping a large amount of product for long periods of time.